Electrical relay with magnetic armature retention means

ABSTRACT

A miniature electric relay is disclosed which includes a header member made of magnetic material. A small permanent magnet is mounted on the header member immediately under the armature such that when the armature is in its de-energized position, one end thereof contacts the permanent magnet and thus completes a low reluctance magnetic circuit having no air gaps therein. When the coil of the relay is energized, the weak strength of the permanent magnet is easily overcome by the magnetic field established by the electric coil and the armature is rotated to cause contact actuation in the usual manner. Once the end of the armature is removed from the permanent magnet and an appreciable air gap exists, the permanent magnet is of sufficiently small strength to cause no appreciable forces on the armature, and thus the presence of the permanent magnet does not require an appreciable stronger coil to overcome its effect. A conventional return spring is provided to return the armature to its deenergized position once the coil is de-energized.

[151 3,656,073 1451 Apr. 1l, 1972 `United States Patent Woodetal.

WITH TURE RETENTION 7 mm mi u, mm

[54] ELECTRICAL RELAY MAGNETIC ARMA MEANS [72] Inventors: Arthur Eastman Wood eagin, Stephen L. King and Kenneth ABSTRACT Rolling Hills; W. Mateer Ralph Edward Marvin, Long Beach; Ralston Everett Bates, Los Alamitos, all of [57] Calif.

.335/203 6 Claims, 2 Drawing Figures FAn-imm n ma 3, 555,073

ARTHUR E. WOOD RALPH E. MARV//v RALsm/v 5 54755 INVENTORS EMR ATTORNEY y gagement with a fixed electrical contact to positionas to provide a return spring and its actuators away from the movable contact. However, inA

g creased by increasing the strength of the fore, very limited in practice.

y restoring force element inherently 1 ELECTRICAL RELAY WITH MAGNETIC ARMATURE RETENTION MEANS This invention relates to electrical relays and more particularly to a miniature electrical relay which includes magnetic means to retain the armature in its de-energized position to prevent contact bounce when the relay is subject to high levels of vibration. ln conventional electrical magnetic relays, an electric coil is energized to establish a magnetic field which causes an armature to rotate from its de-energized position to a second position. A movable electrical contact is positioned in the path of rotation ofthe armature. When the coil is energized, the armature rotates and moves the movable electrical contact into encomplete an electrical circuit. When the ycoil is de-energized, it is usually desirable to provide some means to move the armature back to its de-energized position so that the movable electrical contact breaks contact with the fixed electrical contact. It is the usual practice to provide a second fixed electrical contact to which the movable contact returns by its natural spring action when the armature is returned to its de-'energized position so that the relay may be used as a double throw switch if desired.

The usual way of returning the armature to its de-energized to move the armature situations where high vibratory acceleratioris might beapplied to the relay, any armature unbalance can result in vibratory excitation of the armature against the return spring force, with resultant actuation and the chatter of contacts. The level of vibratory acceleration at which this chatter occurs can be inreturn spring, but this in turn requires additional magnetic force during normal operation of the vrelay to overcome the increased spring strength. The increase in vibration resistance level that can be obtained through such return spring force increase is, therepossible to utilize a permanent spring to provide the restoring to its de-energized position after In larger relays, it has been magnet instead of a return force to return the armature the coil is de-energized. The use of the permanent magnet as a overcomes much of the vibration difficulty mentioned above. Once the armature is returned to its de-energized position and is in physical contact with the magnet, there exists a very low reluctance flux path with no air gap in it. Any permanent magnet which has sufficient strength to restore the armature to its de-energized position when there is an air gap between the magnetic and the armature easily has enough strength to retain the armature against the magnet even when subjected to extremely `high vibration levels, since there is no longer an air gap to increase the reluctance of the magnetic circuit. v

However, the use of a permanent magnet as an armature return member is not feasible in the miniature relays which are in wide spread use today. For example,- in U.S. Pat. No. 3,255,327, assigned to the assignee of the present invention, there is disclosed a miniature electric relay which is in wide spread use today and which has a diameter only of about onethird of an inch and weighs only a fraction of an ounce. ln relays of this small size, it is obviously not feasible to use a permanent magnet as the armature restoring member, since a magnet having-sufficient strength for this purpose would be too large and heavy to use in the tiny relay. Accordingly, in such relays a conventional return spring element hasalways been used to restore the armature to its de-energized position.

lt is accordingly an` object of the present invention to provide an improved electrical relay.

lt is another object of the present invention to provide an improved miniature electrical relay which has` superior vibration withstanding ability.

It is still another object of the present invention to provide an improved miniature electrical relay which utilizes a permanent magnet to retain the armature in its de-energized position.

relay is provided which includes a header member made of I magnetic material. A small pennanent magnet is mounted on the header member immediately under the armature such that when the armature is in thereof contacts the permanent magnet and thus completes a low reluctance magnetic circuit having essentially no air gaps therein. Under these conditions, a small permanent magnet is sufficiently strong to prevent the armature from vibrating even when the relay is subject to quite high vibrational forces and thus prevents any contact bounce or chatter as a result of these vibrations. When the coil of the relay is energized, the weak strength of the permanent magnet is easily overcome by the magnetic field established by the electric coil and the armature is rotated to cause contact actuation in the usual manner. Once the end of the armature is removed from the permanent magnet and an appreciable air gap exists, the permanent magnet is of sufficiently small strength to cause no appreciable forces on the armature, and thus the presence of the permanent magnet does not require an appreciably stronger coil to overcome its effect. A provided to return the annature to its de-energized position once the coil is de-energized. At this time, when the armature is again in contact with the permanent magnet, the permanent magnet again becomes an appreciable factor in the operation of the relay.

For a complete understanding of the invention, together with an appreciation of other object and advantages thereof, please refer to the attached drawings, in which:

FIG. 1 shows a cross-sectional view of a miniature electrical relay in accordance with the present invention;

FIG. 2 shows a sectional view taken along the lines 2-2 of FIG. 1.

Figure 1 shows a cross-sectional view of a miniature electrica l relay 10 which incorporates the presently preferred ernbodiment of the invention. As shown therein, the relay l0 comprises an electrical header assembly l2 and a magnetic actuation or motor assembly 14 which, when energized, causes the desired electrical connections to be made in the header assembly 12.

Electrical header assembly 12 includes the header member 16 which is constructed from a magnetic material such as soft iron or` steel. Header assembly 12 also -in'cludes a movable electrical contact 18 and two fixed electrical contacts 20 and 22. Each of these electrical contacts is connected to a respective contact pin 24, 26 or 28 extending through and insulated from header member 16. The insulation, which may be conventional, is now shown.

The free end of movable contact 18 as positioned between fixed contacts 20 and 22 and the natural spring bias of movable contact 18 maintains its free end in contact with fixed contact v20. This is the de-energized position of the relay and at this time an electrical connection is completed between contact pins 24 and 26. When the relay is energized, as is discussed below, the free end of movable contact 18 is moved downward into contact with fixed contact 22, and at this time electrical connection is completed between contact pins 24 and 28.

The motor assembly 14 includes an electrical coil 30 wound on a bobbin 3l which is mounted on a core 32 and a magnetic frame 34 which includes a pole piece 36 and a plurality of legs 38. An armature 40 is pivotally mounted on pins 42 which are attached to the core 32 to allow armature 40 to pivot about an axis of rotation along one edge of core 32. In FIG. 1 the armature is shown in its de-energized position. When coil 30 is energized, a magnetic field is created between the first end 44 its de-energized position, one end conventional return spring is of armature 40 and pole piece 36 of frame 34. This magnetic field causes the armature to pivot about its pins 42 until end 44 of annature 40 contacts' pole piece 36. This pivoting motion causes the second end 46 of armature 40 to move downward until Contact actuator 48 engages movable contact 18 and moves it downward out of contact with xed contact 20 and into contact with xed contact 22. When coil 30 is deenergized, return spring 50 forces the second end 46 of armature 40 upward away from movable electrical contact 18, and the natural spring action of contact 18 causes it to move away from xed contact 22 and back into engagement with fixed contact 20.

The entire assembly described above is encased in a can 52 which is hermetically sealedto header member 16. The relay as so far described is conventional and is essentially identical to the relay shown in U.S. Pat. No. 3,255,327. However, in accordance with the present invention, a magnetic armature retention assembly is provided which includes a small permanent magnet 54 positioned in a recess in header member 16 just below the first end 44 of armature 40 so that the end 44 contacts the top surface of permanent magnet 54 when the armature is urged into its de-energized position by return spring 50. Once the armature 40 is in this position and is in contact with permanent magnet 54, a low reluctance path exists through permanent magnet 54, the first end 44 of armature 40, core 32, frame 34, leg 38 and header member 16 back to permanent magnet 54 so that a magnet of relatively weak strength will retain the amature 40 in a secure position even when the relay is subjected to quite high vibration forces.

Thus, these high vibration forces do not cause any chatter or` contact bounce between movable contact 18 and fixed contacts and 22.

The polarity of permanent magnet 54 is chosen so that the magnetic flux S6 established by permanent magnet 54 flows through armature 40 in a direction opposite to the flux 58 established by coil 30 when c'oil 30 is energized. In operation, when coil 30 is energized, the flux 58 quickly overcomes the flux 56 in armature 40 and the first end 44 of armature 40 is attracted upwardly into contact with pole piece 36. Once this movement starts and even a small air gap is created between armature 40 and permanent magnet 54, the reluctance seen by permanent magnet 54 increases abruptly, and the flux 56 falls to nearly zero value. At this time, permanent magnet 54 has no appreciable effect on the operation of the relay until coil 30 is again de-energized and the armature is rotated back to its de-energized position by return spring 50.

FlG. 2 shows a cross-sectional view taken along the lines 2-2 of FIG. l and illustrates several additional features of the present invention. The pins 42 upon which armature 40 rotates are attached to leaf spring members 57 which are in turn attached to core 32 through a yoke member 60. The assembly is positioned such that the axes of pins 42 lie along the desired axis of rotation for armature 40. The function of springs 57 is to urge pins 42 continuously into contact with armature 40 so that no air gap ever develops between armature 40 and the pivot edge of core 32 to increase the reluctance of the magnetic path seen by permanent magnet 54 when armature 40 is in its de-energized position.

FIG. 2 also shows two slits 62 cut in the second end 44 of armature 40, thereby defining a tongue 64 between them. The purpose of these slits and the tongue is to provide a weakened section in the end of armature 40 so that it can easily be adjusted by simple bending to permit minor vertical adjustments of armature position in relation to the pole piece 36 while retaining magnetic contact with the permanent magnet 54.

While the invention is thus disclosed and the presently preferred embodiment described in detail, it is not intended that the invention be limited to this shown embodiment. In stead, many modifications will occur to those skilled in the art which lie within the spirit and scope of the invention. Accordingly, it is intended that the invention be limited in scope only by the appended claims.

What is claimed is:

l. An electrical relay comprising:

l. An electrical header assembly, a magnet actuation assembly and a magnetic armature retention assembly; 2. said electrical header assembly comprising:

a. a support header member constructed of magneticl material and having a plurality of contact pins extending therethrough b. a stationary electrical contact connected to one of said contact pins;

c. a movable electrical contact having its first end connected to another one of said contact pins and having its other end positioned adjacent to said stationary contact and normally not contacting said stationary confact;

3. said magnetic actuation assembly comprising:

a. a magnetic frame including a two legs;

b. a magnetic core having a first and second end, said first end being attached to said frame and said second end being spaced from said pole piece;

c. a coil, said coil being mounted around said co're;

d. an armature having a first and` second end;

e. means for mounting said armature for rotation about an axis of rotation adjacent to said second end of said core; said armature beingrotatable between a first position in which said first end of said armature is in contact with said pole piece of said frame and a second position in which said first end is spaced from saidpole piece,.thereby providing a first magnetic circuit comprising said core, said pole piece and said first vend of said armature in which magnetic flux is established when said coil is energized;

4. said magnetic circuit assembly being mounted to said electrical header assembly by attachingsaid legs of said frame to said support header member so that said movable electrical contact is in the path of rotation of said second end of said armature such that when said armature is in its first position, said second end of said armature moves said movable electrical contact into contact with said stationary contact; a

5. said magnetic armature retention assembly comprising a permanent magnet mounted on vsaid support header member beneath said first end of said armature such that said first end of said armature contacts said permanent magnet when said armature is in its second position, thereby providing a secondmagnetic circuit comprising said permanent, magnet, said first end of said armature, said core, said legs of said magnetic frame and said support header member in which magnetic flux is established by said permanent magnet; and

6. biasing means for urging said armature into its second position when said coi-l is de-energized'.

2. The electrical relay of claim 1 in which the polarity of said permanent magnet and said coil are selected such that the flux established in said first end of said armature by said coil is of opposite polarity to the flux established in said first end of said armature by said permanent magnet.

3. The electrical relay of claim 2 in which said armature is pivotally mounted on pins connected to said second end of said core and which further includes spring biasing means for holding said pin in contact with said armature to bias said armature against said second end of said core so that no air gap exists between said armature and said second end of said core.

4. The electrical relay of claim 3 which further includes slits in said first end of said armature to facilitate adjusting said ar. mature relative to said pole piece when said first end contacts said permanent magnet whenever said armature is in its second position.

5. The electrical relay of claim 4 in which said electrical header assembly includes first and second stationary electrical contacts connected to respective first and second ones of said contact pins, said first and second stationary contacts being spaced apart, and in which said other end of said movable electrical contact is positioned between said first and second stationary contacts and normally contacting said first contact.

pole piece and at least 6. The electrical relay of claim 5 in which said biasing means for urging said armature into its second position com-l prises a return spring member having one end attached to said support header member and having its other end contacting said second end of said armature, 5 

1. An electrical relay comprising:
 1. An electrical header assembly, a magnet actuation assembly and a magnetic armature retention assembly;
 2. said electrical header assembly comprising: a. a support header member constructed of magnetic material and having a plurality of contact pins extending therethrough b. a stationary electrical contact connected to one of said contact pins; c. a movable electrical contact having its first end connected to another one of said contact pins and having its other end positioned adjacent to said stationary contact and normally not contacting said stationary contact;
 3. said magnetic actuation assembly comprising: a. a magnetic frame including a pole piece and at least two legs; b. a magnetic core having a first and second end, said first end being attached to said frame and said second end being spaced from said pole piece; c. a coil, said coil being mounted around said core; d. an armature having a first and second end; e. means for mounting said armature for rotation about an axis of rotation adjacent to said second end of said core; said armature being rotatable between a first position in which said first end of said armature is in contact with said pole piece of said frame and a second position in which said first end is spaced from said pole piece, thereby providing a first magnetic circuit comprising said core, said pole piece and said first end of said armature in which magnetic flux is established when said coil is energized;
 4. said magnetic circuit assembly being mounted to said electrical header assembly by attaching said legs of said frame to said support header Member so that said movable electrical contact is in the path of rotation of said second end of said armature such that when said armature is in its first position, said second end of said armature moves said movable electrical contact into contact with said stationary contact;
 5. said magnetic armature retention assembly comprising a permanent magnet mounted on said support header member beneath said first end of said armature such that said first end of said armature contacts said permanent magnet when said armature is in its second position, thereby providing a second magnetic circuit comprising said permanent magnet, said first end of said armature, said core, said legs of said magnetic frame and said support header member in which magnetic flux is established by said permanent magnet; and
 6. biasing means for urging said armature into its second position when said coil is de-energized.
 2. said electrical header assembly comprising: a. a support header member constructed of magnetic material and having a plurality of contact pins extending therethrough b. a stationary electrical contact connected to one of said contact pins; c. a movable electrical contact having its first end connected to another one of said contact pins and having its other end positioned adjacent to said stationary contact and normally not contacting said stationary contact;
 2. The electrical relay of claim 1 in which the polarity of said permanent magnet and said coil are selected such that the flux established in said first end of said armature by said coil is of opposite polarity to the flux established in said first end of said armature by said permanent magnet.
 3. The electrical relay of claim 2 in which said armature is pivotally mounted on pins connected to said second end of said core and which further includes spring biasing means for holding said pin in contact with said armature to bias said armature against said second end of said core so that no air gap exists between said armature and said second end of said core.
 3. said magnetic actuation assembly comprising: a. a magnetic frame including a pole piece and at least two legs; b. a magnetic core having a first and second end, said first end being attached to said frame and said second end being spaced from said pole piece; c. a coil, said coil being mounted around said core; d. an armature having a first and second end; e. means for mounting said armature for rotation about an axis of rotation adjacent to said second end of said core; said armature being rotatable between a first position in which said first end of said armature is in contact with said pole piece of said frame and a second position in which said first end is spaced from said pole piece, thereby providing a first magnetic circuit comprising said core, said pole piece and said first end of said armature in which magnetic flux is established when said coil is energized;
 4. said magnetic circuit assembly being mounted to said electrical header assembly by attaching said legs of said frame to said support header Member so that said movable electrical contact is in the path of rotation of said second end of said armature such that when said armature is in its first position, said second end of said armature moves said movable electrical contact into contact with said stationary contact;
 4. The electrical relay of claim 3 which further includes slits in said first end of said armature to facilitate adjusting said armature relative to said pole piece when said first end contacts said permanent magnet whenever said armature is in its second position.
 5. The electrical relay of claim 4 in which said electrical header assembly includes first and second stationary electrical contacts connected to respective first and second ones of said contact pins, said first and second stationary contacts being spaced apart, and in which said other end of said movable electrical contact is positioned between said first and second stationary contacts and normally contacting said first contact.
 5. said magnetic armature retention assembly comprising a permanent magnet mounted on said support header member beneath said first end of said armature such that said first end of said armature contacts said permanent magnet when said armature is in its second position, thereby providing a second magnetic circuit comprising said permanent magnet, said first end of said armature, said core, said legs of said magnetic frame and said support header member in which magnetic flux is established by said permanent magnet; and
 6. biasing means for urging said armature into its second position when said coil is de-energized.
 6. The electrical relay of claim 5 in which said biasing means for urging said armature into its second position comprises a return spring member having one end attached to said support header member and having its other end contacting said second end of said armature. 